Technical Abstract:
Two-year crop rotations, consisting of barley/clover, canola, green bean, millet/rapeseed, soybean, sweet corn, and potato, all followed by potato, were established in replicated field plots in Newport, ME, in 1997 and 1998 (both rotation entry points present each year) and continued each year thereafter. In 2002, plots were split to include a fall cover crop (winter rye planted without tillage) on half of each plot as an additional factor. Subsequent potato crops were evaluated for soilborne diseases, and soil microbial characteristics were determined based on soil microbial populations, substrate utilization, and fatty acid methyl ester (FAME) profiles. Crop rotations had significant effects on soilborne diseases and soil microbial characteristics, with canola and rapeseed rotations consistently reducing Rhizoctonia diseases and common scab and resulting in increased microbial activity and unique soil microbial profiles. Addition of a cover crop resulted in overall increased ground cover, significant effects on soil microbial characteristics, and overall reductions in the soilborne tuber diseases black scurf and common scab across all rotations. Average reductions in disease severity for the different rotations ranged from 1 to 19% (12.5% avg) and 0 to 21% (7.2% avg) for black scurf and common scab, respectively. The combined effect of a rapeseed rotation and winter rye cover crop reduced disease severity by 41% for black scurf and 33% for common scab relative to continuous potato with no cover crop. Thus, in addition to positive effects in reducing erosion and improving soil quality, cover crops may provide additional aid in the management of soilborne pathogens and, in conjunction with effective crop rotations, can have an important role in sustainable potato cropping systems.